Lake Toba (Indonesian: Danau Toba) is a large natural lake occupying the caldera of a supervolcano. The lake is about 100 kilometres (62 mi) long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. Located in the middle of the northern part of the Indonesian island of Sumatra, with a surface elevation of about 900 metres (2,953 ft), the lake stretches from to . It is the largest lake in Indonesia and also the largest volcanic lake in the world.
Lake Toba is the site of a massive supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago,representing a climate-changing event. It is the largest known explosive eruption on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences for human populations; it killed most humans living at that time and is believed to have created a population bottleneck in central east Africa and India, which affects the genetic make up of the human worldwide population to the present.